Utilizing two model cytotoxic thymus-derived lymphocyte systems, we propose to establish the biochemical and biological rules by which identification of antigens can be made which cytotoxic T lymphocytes (CTLs) recognize. The two systems are: CTLs specific for the expression of the glycoprotein of vesicular stomatitis virus and CTLs which recognize the H-2K and H-2D gene products. The identification of antigens recognized by these CTL populations will be approached in two ways. First, we will establish the minimal requirements for eliciting CTLs and the specificity of the resultant effector cells. Second, we will inhibit CTL-target cell conjugate formation. These approaches will not only help in the identification of other antigens of interest, but may also lay the foundation for studies directed toward antigen presentation and receptor analysis.